Centrifugal pump discharge vs. speed at constant head and geometry Assume impeller diameter and system head remain the same. Describe how discharge varies with rotational speed. Choose the correct relation.
Mechanical Engineering
Hydraulic Machines
Difficulty: Easy
Choose an option
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ADischarge is directly proportional to speed (Q ∝ N)
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BDischarge varies as the square of speed (Q ∝ N²)
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CDischarge is independent of speed
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DDischarge decreases as speed increases
Answer
Correct Answer: Discharge is directly proportional to speed (Q ∝ N)
Explanation
Affinity law (similarity)
- For geometrically similar operation of a given impeller, Q ∝ N, H ∝ N², and P ∝ N³ (with diameter fixed).
ThereforeAt constant head/geometry, increasing speed raises discharge in direct proportion.
Final AnswerQ ∝ N (directly proportional).